Gearing of ctjt-off valves for steam-engines



' vention, we will proceed to describe its oon- UNITED STATES PATENTOFFICE.

P. W. GATES, D. R. FRASER, AND THOMAS CI-IALMERS, OF CHICAGO, ILLINOIS.

GEARING OF CUT-OFF VALVES FOR STEAM-ENGINES.

Specification of Letters Patent No. 21,668, dated October 5, 1858.

T 0 aZZ whom t may concern:

Be it known that we, P. W. GATES, D. R. FRASER, and THOMAS CHALMERS, allof i Chicago, in the county of Cook and State of Illinois, have inventeda new and useful Improvement in Variable-Cut-Oif Gear for Steam-Engines;and we do hereby declare that the following is a full, clear, and exactdescription of the same, reference being had to the accompanyingdrawings, forming part of this specification, in which- Figure l, is alongitudinal central section of part of the cylinder and valve-chest ofa horizontal steam-engine, exhibiting the application of ourimprovement. Fig. 2, is a plan of all the parts below the line w, inFig. l.

Similar letters of reference indicate corresponding parts in bothfigures.

This invention consists in certain improved mechanism for operating twocut-off valves which are applied to the back of a slide valve whicheHects the induction and eduction of steam to and from an engine andwhich is capable of liberating the said cut-o valves at such point inthe stroke of the engine-piston as may be determined by the operation ofa governor or by a permanent adjustment as to allow them to be closedinstantaneously to cut off the steam from the cylinder, either by thepressure of steam in the valve-chest or by other suitable means.

To enable others to make and use our instruction and operation.

A, is the cylinder; B, is the valve chest.

a, a, are the steam ports, and Z7, the eX- haust port of the cylinder.

'C, is the main slide valve of the kind known as the short slide, havingtwo passages c, c, through it of a size to correspond with the ports a,a', and the usual exhaust cavity CZ, in its face. This valve has twostems e, e, one at each end, which pass through the ends of the valvechest and are packed by stuffing boxes f, f, therein and it may beoperated by an eccentric or in any other well-known manner.

D, D, are the two cut-off valves consisting of solid plates fitted toslide on the back of the valve and provided with separate stems g, g,passing through stuffing boXes L, h',

in the ends of the valve chest. These are furnished outside the valvechest with crossheads i, z", which work on fixed guide rods j, j, and j,y, and which carry two pawls c, 7c', one each, which pawls are capableof engaging respectively in notches Z, Z, in two blocks m, m, attachedto the stems e, e', of the main valve. The said pawls have springs fn,a, applied to force them into the notches as they arrive over them, andthrough their aid the cut-oft' valves are caused to be moved by andalong with the main valve.

p, p, are two metal slides, fitted to slide in grooves g, g', in thetops of the heads m, m', and under the pawls 7c, c, for the purpose ofthrowing said awls out of the notches to allow the cut-o valves to bemoved by the pressure of steam to proper positions to cut off the steamfrom the ports a, a', by the pressure of steam from in the steam-chestacting opposite to their stems g, g. These two slides pass freelythrough the crossheads i, z", and are connected rigidly with two toothedrack bars r, r, which work in guides s, s', on the top of thesteam-chest and which gear on opposite sides of a pinion t, on a shaftu, which works in suitable bearings in a stand E, ereceted above thevalve-chest. This shaft u, when turned, moves the rackbars in oppositedirections and serves to adjust the two slides p, p', to throw out thepawls Z0, 7c', from the notches Z, Z, and thus disconnect the cut-offvalves from the main valve earlier or later in the stroke of the piston.The said shaft might be adjusted by hand to cut olf at any point in thestroke that may be desired, but I have represented it and prefer to useit in connection with a governor, and to this end I employ upon itanother pinion t', or extend the same pinion t, to a sufficient lengthto gear with a toothed rack o, on the regulating rod fw, of the governorGr. The stand E, which contains the bearings of the shaft u, also servesto support the governor. y, y, are stops attached to the guide rods j,j, for the purpose of arresting t-he crossheads of the cut-off valvesand thereby stopping the said valves in proper' position for the pawlsc, Za', to take hold of them as the main valve completes its stroke.These stops y, y, and y, y', are made hollow to contain india-rubbercushions and the cross-heads are furnished with piston-like projections0, 0, and o', 0', to come in Contact with the rubber cushions to preventviolent concussions when the valves are thus arrested. The heads m, m',of the main valve stems are also provided with cavities Z, Z, (Fig. l)at the backs of which are india-rubber cushions 3, 3*, against whichstrike the ends of piston-like projections 4, 4*, on the crossheads z',z', to stop the cutoff valves in positions to close the ports 0, c',when they return after their pawls have been liberated .from the mainvalve stem.

To illustrate more fully the operation of the cut-oi:l gear, I willfirst suppose the slide valve to be in the position shown in Figfl,moving to the right hand as indicated by the arrow on one of its stems.It will be seen that the cut-off valve D is l locked to the main valveby its pawl 7c, in a position to leave the port c, open, and the othervalve D', is free of the main valve C, and supposed to be stopped by thestops y', y', shown in Fig. 2 and the passage c', of the main valve. isbeing uncovered by the movement of C. Steam is being admitted to thecylinder through c, a, and exhausted through a', d. The pawl la, of thevalve D, is just being brought by the simultaneous movement of thevalves C, D, into Contact with the slide p, and about to be raised outof the notch Z; and as soon as this takes place, the valve D, will beinstantaneously driven by the pressure of the steam opposite its rod,over the passage c, and the steam is thus cut cttl from the port a,during the ref mainder of the stroke of the main valve C. As the mainvalve C completes its stroke, the notch Z', coming under the pawl le,connects the cut-off valve D', and locks it so that the passage c', willremain open during its return stroke till the pawl Z0', is disengaged bycoming in contact with the slide p'. During so much of the return strokeof the valve C, as leaves the passage c, in communication with the port(Z, t-he said passage remains covered by the valve D; but the movementof the valve C being continued beyond the point where it closes the porta, the valve D is stopped by the stops y, and the so-continued movementof the valve C, uncovers the top of the passage c, and

brings the notch Z, in the head m, of the stem e, under the pawl 7c,which then drops in and locks it.. The disengagement of the pawl c-, asabove mentioned allows the steam to act upon the valve D', to make itcover 50 the passage 0', in the same manner that the disengagement ofthe pawl Ze, caused the valve D to close the passage c, as beforedescribed. In this way the operation proceeds; the operation of thecut-off valves being the reverse in the opposite strokes of the mainvalve. As the governor rises, t-he slides p, p', are moved apart; and asit falls they are drawn toward each other; in the rst case causing thecut-oli' valves to be liberated and allowed to cover ,the ports 0, c',earlier, and in the latter case later, in the stroke of the piston. Orthe shaft u, may be adjusted by hand, and set to cut olf permanently atsuch point in the stroke as may be desired.k The same mechanism may beused with two cut-ofi valves applied each to one of twov separate mainvalves, the said main valves being arranged near the ends of thecylinder in separate steam chests or in the same one, both of whicharrangements are well known; or it may be used in combination with twocut-otf valves working onv a stationary partition plate which separatesthem from the main valves.

What we'claim as our invention, and desire'tosecure by Letters-Patent,is

Vorking the cut-olip valves D, D', in combination with a main slidevalve C or separate main slide valves of the character described, bymeans of the pawls 7c, lc', to lock the cut-oiil valves with the mainvalve or valves in an open condition, the variable or adjustable slidesp, 29', to disengage the said pawls, the stops 3, 3*, to stop the saidcutoff, valves in a closed condition after their liberation, vand stopsy, y, y', y', to stop and o-pen them by the completion of the stroke oft-he main valve or valves; the whole operating substantially asdescribed. 90

P. W. GATES.

D. R. FRASER. THOMAS CI-IALMERS. Witnesses:

I. L. FARGO, A. Gr. WARNER.

